It's been the coolest summer in 14 years.
The National Weather Service said Friday that average temperatures during July and August were about 4 degrees below normal in downtown Los Angeles and about 1 1/2 degrees below normal in the San Fernando Valley.
"That's not real dramatic, but it's been enough so people notice," said Tim McClung, a Weather Service meteorologist.
And it has helped to keep air conditioners turned off to avoid any more power blackouts in energy-conscious California.
There are several reasons why it's been the coolest summer since 1987, but none of them has anything to do with such widely discussed meteorological phenomena as global warming or the expected return of El Nino this winter, McClung said.
"It's just how the weather patterns set up," he said.
McClung said the average temperature in downtown Los Angeles in July was 71 degrees, 3.9 degrees below the normal average of 74.9. The average in August was 72 degrees, 4 degrees below the average of 76.
The Valley average in July was 73.1 degrees, 2.8 degrees below the normal of 75.9. The average in August was 76.1, half a degree below the normal of 76.6.
These averages are computed by adding the maximum and minimum readings for each day, dividing by 2 and averaging the totals.
In one of those strange twists of meteorological irony, one of the main reasons it's been cooler than usual is that it's been hotter than usual in the desert. The inland heat sets up an interaction with the cool Pacific waters along the coast.
McClung said ocean temperatures off Southern California have been a couple of degrees cooler than usual this summer, and that has kept coastal air temperatures cool too.
On Friday, the air and water temperatures at the beach in Santa Monica were in the upper 60s. On the other hand, temperatures have been soaring in the deserts. In Palm Springs, the thermometer peaked at 103 degrees Friday.
Cool air is denser than hot air, so air tends to flow from cooler areas to warmer areas. With a temperature differential often reaching 40 degrees or more, the onshore flow of cool, damp air from the Pacific has been especially persistent this summer.
On a lot of days, this dank air has been piling up against the coastal slopes of Southern California as fog and clouds. Morning sunshine starts burning away the overcast, but the closer to the coast, the later it has been before the skies begin to turn sunny and temperatures begin to rise.
